In contrast to the state of the field 10 years ago, the understanding of disease pathogenesis and the treatment goals for patients with psoriasis have changed enormously. A 75% improvement in the Psoriasis Area and Severity Index (PASI 75) is no longer the desirable treatment goal for dermatologists or for disease-experienced patients with plaque-type psoriasis. Physicians and patients now demand a PASI 90 or even a PASI 100. Identification of interleukin (IL)-17 and IL-23 as key mediators in the pathogenesis of psoriasis and the development of new biologics that target these pathways are major steps toward disease control. 1 By targeting cytokines, a clear or almost clear disease status became an achievable goal in a substantial number of patients. The molecular and cellular mechanisms that underlie disease milestones in psoriasis treatment have not yet been fully elucidated, and we remain far from a permanent cure. In particular, we are missing the biomarkers and molecular indicators of forthcoming psoriasis flares in patients who show no or minimal disease activity. This is critical information for identifying the appropriate point in time to discontinue a systemic medication in an individual who has achieved disease control.What has changed since the introduction of tumor necrosis factor blockers as successful biologics for psoriasis? Research in dermatology uncovered the immunopathology of psoriasis and unveiled psoriasis as the prototypic subtype 17 helper T cell (Th17)-mediated autoimmune disease in humans, with IL-17-and IL-22-producing T cells being key inflammatory mediators. 1 Contrary to our thinking at the beginning of this millennium, Th1 cells and interferons seem to be less important in psoriatic skin inflammation. 2 Cytokines are responsible for many results in psoriasis, including altered proliferation and activation of keratinocytes and endothelia. IL-17A together with IL-22 and tumor necrosis factor regulate the secretion of factors like antimicrobial peptides (eg, human β-defensin 2) or epithelial mediators (eg,.The most critical factor for Th17-dependent autoimmune disease, however, is IL-23. Although IL-17A expression can occur in the absence of IL-23, the phenotype and pathogenicity of IL-23-generated Th17 cells are different. 3 In psoriasis, monoclonal antibodies (mAbs) that are directed against IL-17A, IL-17RA, or IL-17A/F but also neutralization of IL-23 all show high efficacy. 1 Interleukin 23 is composed of 2 units, p19 and p40. The latter unit, together with p35, forms IL-12. A mAb that is directed toward IL-12/IL-23p40 (ustekinumab) was introduced years before mAbs against IL-17A or IL-23p19 were approved. Data from indirect comparison and head-to-head